Transformer



F 1940. M. w. HUMPHREYS 2,191,393

TRANSFORMER Filed Nov. 23, 1937 IN VEN'IFOR. M/Q/P/O/Y M #(MPH/PE n5fate f/mm f/ ATTORNEYfi Patented Feb. 20, 1940 UNITED STATES PATENT.OFFICE 3Claims.

This invention relates to electric transformers, and has particularreference to the transformer core and to the method of making the same.

The principal object of the invention is to eliminate the necessity formaking core stampings, to avoid the loss by way of scrap incident to thepunching of the stampings or laminae, to eliminate the expense incidentto the assembly of stamped laminations, and to provide a transformerhaving a core which is so formed as to provide improvement in themagnetic path and increased efliciency.

In accordance with the present invention, the core, instead of beingbuilt up of a large number of iron stampings, as is customary, is madefrom strip material which is wound in superposed layers and generallyfrom one continuous iron strip. Preferably the core is wound from stripmaterial through the coils until an annulus of proper thickness is builtup, and subsequently the initial annular shape of the core may bechanged by bending the core in a press or by other suitable means to arelatively flat or oblong shape.

The invention may be further briefly summarized as consisting in certainsteps of the improved method and in the improved transformer which willbe described in the specification and set forth in the appended claims.

In the drawing which illustrates the principle of the invention.

Fig. 1 is a view illustrating the manner in which the core is initiallyproduced in the form of an annulus from core-forming material in theform of a continuous strip;

36 Fig. 2 is a side view of a transformer with parts in section,illustrating by way of example a form in which the transformer core maybe eventually shaped;

Fig. 3 is a sectional view substantially along the line 3--3 of Fig. 2;and

Fig. 4 is a sectional view substantially along the line 4-4 of Fig. 2.

As is well known, transformers require laminated cores built up fromstampings punched from sheet iron or other suitable sheet metal,

with considerable loss by reason of scrap material, and these punchingsor stamped laminations are subsequently assembled to the desired coreshape with the primary and secondary coils or coil sections in properrelation on portions of the core. In accordance with the presentinvention, the use of stampings is entirely eliminated and the laminatedcore is built up by winding a coreforming strip through the coils intothe form of so an annulus, the winding being continued until there aresufiicient superposed layers to form a laminated core having therequired cross-section. Although the core may, if desired, be retainedin the shape of an annulus, it is generally flattened to oblong shape,leaving straight legs to accom- 6 modate the coils and more or lesssemi-circular ends.

The particular design of the transformer so far as insulation and coilsare concerned is quite immaterial to the invention, but in Figs. 2, 3,and 10 4 I have shown a transformer produced by my improved method. Thistransformer has a core formed in accordance with the present invention,and, in addition, one primary and two secondaries and two magneticchokes or shunts. How- 15 ever, it is to be understood that thesefeatures and the transformer design so far as the coils and chokes areconcerned are not essential to the present invention. The transformerillustrated has an elongated core it which is continuous in the respectthat it is built up of a continuous strip of core-forming material, suchas soft iron. This core, as illustrated, has two parallel legs androunded ends. On one of the legs is positioned a primary coil II and twosecondary coils II but, 25 of course, in some instances there may be asingle secondary as well as a single primary, or the primary andsecondary windings may be otherwise made sectional. In this instancealso the transformer has two magnetic shunts I3 30 formed fromsubstantially c-shaped stampings which are hooked over the parallel legsof the core and extend down along one side thrreof. The shunts and coilsare provided with suitable insulation which per se is immaterial to thepres- 35 cut invention, the principal feature of which is the method bywhich the core is formed.

As previously stated, the core is formed from a continuous strip of ironor other core-forming material which is wound in the form of an annulusthrough the coils. In Fig. 1 I have shown in simplified manner a fixturein which this can be done. In this view the strip of core-formingmaterial is indicated at I4. It iswoundin the form of an annulus l5through the previously formed 45 primary and secondary coils of whichthere may be two or more. The coils may be supported in a suitablestationary part It of the fixture which includes. a standard II, thecoils being held stationary while the annulus is rotated through the 50coils while the strip is fed thereon until the annulus has assumed thedesired thickness. In this instance the annulus is supported at itsinner periphery by rollers ll which may be rotatably supported in fixedposition on suitable arms ll of the fixture. The annulus may be rotatedin move outwardly to accommodate the constantly increasing thickness ofthe annulus. There may be as many of these supporting and drivingrollers as desired, and power may beapplied to them in any suitablefashion, but preferably a from a single driving member from which powermay be transmitted to the rollers 20 by shafts made flexiblelay-universal joints or otherwise.

The mechanical driving means for this purpose is not illustratedss itmay assume various forms and per se constitutes no part of the presentinvention.

To start the core, the strip may be strung through the primary andsecondary coils or coil sections until the first layer is completed andthe inner end may then be fastened to the innermost complete convolutionby spot-welding or soldering, the band so formed then resting upon theinner rollers l8 and being engaged by the outer radially movable drivingrollers 20. Then the rotation of the rollers III is started and thisband is thereby rotated, feeding the strip H thereon and graduallybuilding it up until, as before stated, an annulus of proper thicknessis formed, whereupon the rotation is stopped. The strip, I4 will be heldunder any desired tension so that the superposed convolutions will be inclose engagement. After the core is built up to the proper thickness andthe rotation of the driving rollers is stopped, the outer layer .orconvolution is cut from the strip l4 and the outer free end may befastened to the outermost complete convolution by spot-welding orsoldering. Next the core in the shape of an annulus with the coils isremoved from the fixture.

It is unnecessary in all instances to change the shape of the core, butin case it is desired to change its shape, for example, to the oblong orflattened shape illustrated in Fig. 2, this can be done in a suitablepress or byother suitable pressing means, the coils of course beingfirst suitably arranged with respect to each" other. Then, if magneticchokes such as those-illustrated are desired in any particulartransformer, these can be added without difficulty.

I regard the transformer core formed of a continuous strip or from stripmaterial wound through the coils in superposed convolutions or layers asbeing more suitable from the standpoint of emciency than a core formedfrom eeparate stampings, and, additionally, the expense incident toproducing the stampings, the loss in scrap, and the expense incident toassembling the stampings are avoided. It will be seen therefore that theobjects stated at the beginning of the specification are accomplishedvery eifectively.. I do not desire to be confined to either thetransformer design or the precise steps of the method hereinillustrated, butaim in my claims to cover all modifications which do notinvolve a departure from the spirit and scope of the invention. Y

Having thus described my invention, I claim:

1. The method of forming a transformer composed of coils and a corewhich consists in feeding a strip of core-forming material through thecoils thus forming an annulus, supporting the annulus interiorly thereofat a plurality of circumferentially spaced points and at the same timeholding the coils in definite position, and applying friction drivingmeans to the annulus at a plurality of circumferentially spaced pointsthereby rotating the annulus and causing a predetermined number ofconvolutions to be built up withthe strip being fed onto the outerperiphery of the annulus.

2. The method of forming a transformer composed of primary and secondarycoils and a core, which comprises supporting the coils in fixed andspaced relation around a central point, feeding core-forming material inthe form of a substantially flat strip successively through the openingsof the coils so as to form an annulus with the strip extending crosswiseof the coil openings over the inner edges thereof, and retating theannulus to wind the strip thereon so as to build it up toward the outeredges of the coil openings with the convolutions superposed upon eachother in a radial direction until a core of the desired thickness isobtained.

3. The method of forming a transformer composed of primary and secondarycoils and a core, which comprises supporting the coils in fixed andspaced relation around a central point, feeding core-forming material inthe form of a substantially flat strip successively through the openingsof the coils so as to form an annulus with the strip extending crosswiseof the coil openings over the inner edges thereof, supporting theannulus at its inner periphery, and rotating the annulus to wind thestrip thereon so as to build it up toward the outer edges of the coilopenings with the convolutions superposed upon each other in a radialdirection until a core of the desired thickness is obtained.

MARION W.

